Data from: Age-specific breeding success in a wild mammalian population: selection, constraint, restraint, and senescence

The Selection, Constraint, Restraint, and Senescence Hypotheses predict how breeding success should vary with age. The Selection Hypothesis predicts between-individual variation arising from quality differences; the other hypotheses predict within-individual variation due to differing skills or physiological condition (Constraint), residual reproductive lifespan (Restraint), or somatic and reproductive investment (Senescence). Studies tend to focus on either the initial increase in breeding success or later decrease; however, both require consideration when unravelling the underlying evolutionary processes. Additionally, few studies present genetic fitness measures, and rarely for both sexes. We therefore test these four hypotheses, which are not mutually exclusive, in a high-density population of European badgers Meles meles. Using an 18-year dataset (including 22 microsatellite loci) we show an initial improvement in breeding success with age, followed by a later and steeper rate of reproductive senescence in males than in females. Breeding success was skewed within age-classes indicating the influence of factors other than age-class. This was partly attributable to selective appearance and disappearance of badgers (Selection Hypothesis). Individuals with a late age of last breeding showed a concave down relationship between breeding success and experience (Constraint Hypothesis). There was no evidence of abrupt terminal effects; rather, individuals showed a concave down relationship between breeding success and residual reproductive lifespan (Restraint Hypothesis), with an interaction with age of first breeding only in females. Our results demonstrate the importance of investigating a comprehensive suite of factors in age-specific breeding success analyses, in both sexes, in order to fully understand evolutionary and population dynamics.

选择假说（Selection Hypothesis）、约束假说（Constraint Hypothesis）、限制假说（Restraint Hypothesis）与衰老假说（Senescence Hypothesis）共同阐释了繁殖成功率随年龄变化的规律。其中选择假说预测了源于个体质量差异的个体间繁殖成功率变异；其余三类假说则分别对应不同的个体内繁殖成功率变异成因：技能或生理状态差异对应约束假说、剩余繁殖寿命对应限制假说，体细胞与繁殖投资的权衡对应衰老假说。现有相关研究往往仅聚焦于繁殖成功率的早期提升阶段，或是后期的下降阶段，但在解析其背后的演化进程时，需同时兼顾这两方面的变化。此外，鲜有研究同时报道遗传适合度指标，且极少兼顾两性个体。为此，我们以高密度种群的欧洲獾（Meles meles）为研究对象，对这四个并非互斥的假说展开验证。基于包含22个微卫星位点的18年观测数据集，我们发现繁殖成功率随年龄先呈上升趋势，随后进入生殖衰老阶段，且雄性的生殖衰老速率较雌性更快且更为陡峭。同年龄组内的繁殖成功率存在偏态分布，这表明除年龄组外，其他因素同样会对繁殖成功率产生影响。该现象部分可归因于獾个体的选择性出现与消失（选择假说）。末次繁殖年龄较晚的个体，其繁殖成功率与繁殖经验之间呈向下凹的曲线关系（约束假说）。未发现存在突发性终端效应的证据；与之相反，个体的繁殖成功率与剩余繁殖寿命之间同样呈向下凹的曲线关系（限制假说），且仅在雌性个体中，该关系与首次繁殖年龄存在交互效应。本研究结果表明，若要全面解析演化与种群动态机制，在针对两性的年龄特异性繁殖成功率分析中，需综合考量多类影响因素。